Marine-derived bioactive compounds from seaweeds as anti-inflammatory agents: a systematic review of molecular mechanisms and therapeutic potential

Chronic inflammation plays a central role in the development of numerous degenerative diseases, including cardiovascular disorders, diabetes, cancer and neurodegenerative conditions. Although conventional anti-inflammatory drugs, such as NSAIDs and corticosteroids, are widely used, their long-term use is often associated with significant adverse effects, prompting interest in safer natural alternatives. Marine macroalgae (seaweeds) are recognized as rich sources of structurally diverse bioactive compounds, including sulphated polysaccharides, polyphenols, sterols, and carotenoids, with promising anti-inflammatory properties. However, a comprehensive synthesis linking these compounds with their molecular mechanisms remains limited. This systematic review aimed to identify seaweed-derived bioactive compounds with anti-inflammatory activity and analyse their molecular mechanisms. The review was conducted in accordance with the PRISMA 2020 statement, using a structured Boolean search string applied to the Scopus database for records published between 2015 and 2025. After screening and eligibility assessment, 41 publications met the inclusion criteria. Three reported findings for more than one compound or species, yielding 44 compound-level entries. Methodological quality was appraised using the Mixed Methods Appraisal Tool (MMAT), adapted to the heterogeneous designs represented (in vitro, in vivo, in silico and clinical); all included studies met a quality threshold of at least 80% of applicable criteria. Key compounds – fucoidan, phlorotannins, fucoxanthin, alginate, ulvan, and fucosterol – were found to suppress inflammatory mediators (NO, TNF-α, IL-1β, IL-6) by modulating major signalling pathways, including NF-κB, MAPK, the NLRP3 inflammasome, and TLR4 signalling. Overall, seaweeds represent promising sources of natural anti-inflammatory therapeutics, though the evidence base remains dominated by preclinical studies and would benefit from standardized reporting and broader database coverage in future reviews.